Such a type of cylinder device having a force multiplier has been conventionally disclosed in Patent Literature 1 (Japanese Patent Application Publication, Tokukai, No. 2014-240117). This conventional technique is configured as follows.
An advancing-retracting first piston and a force-multiplying second piston are arranged in series in a vertical direction in a housing. Upward force acting on the second piston due to locking pressurized fluid is multiplied and converted into multiplied downward force, and the multiplied downward force is transmitted to an output rod. Further, in an air passage for use in detection formed in an upper wall of the housing, a detection valve is provided. The detection valve includes a detection rod slightly protruding downward from the upper wall. Then, when the second piston rises to a position in the vicinity of an upper limit position beyond a locking area from a release position, the second piston abuts on the detection rod. Subsequently, the second piston pushes up the detection rod from the position in the vicinity of the upper limit position until the detection rod reaches the upper limit position. This opens the detection valve.